Convertor for continuously melting scrap with tapping means

ABSTRACT

In a process for continuously melting scrap (6) and/or pig iron within a converter (1), the converter (1) is heated in proximity of the bottom (3) with sub-stoichiometric burners (4), having their flames (5) essentially radially directed into the interior of the converter (1). In this case, secondary air or O 2  is supplied at a distance above the burner plane for the purpose of completing the combustion. The melt is, optionally together with slag, discharged via a tapping means (9) laterally connected to the converter (1) into a mobile ladle (19). For the purpose of interchanging ladles (19), the converter (1) is swivelled into a position in which the level of the melt is located below the taphole (11).

This is a division of Application No. 07/278,543, filed Dec. 1, 1988 nowU.S. Pat. No. 4,895,594.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention refers to a process for continuously melting scrap and/orpig iron within a converter as well as to an apparatus for performingthis process.

2. Description of the Prior Art

There are already known allothermic converter processes in which scrapis preheated and/or molten, noting that such processes are optionallyperformed with the addition of pig iron. Expensive tiltable furnaceshave been proposed for performing such processes, noting that asubstantial drawback of the known processes resides in the fact thatthey are discontinuously operated in batches, because the cruciblecomprises no devices whatsoever for continuously discharging the moltenmaterial.

Heating of the known allothermic furnaces for preheating scrap and/ormolten material is, as a rule, effected by means of bottom nozzlesblowing mixtures of carbon and oxygen into the bottom pool or by meansof blowing fuels together with oxygen via a lance introduced from above.

The so-called KVA-process is performed with a metallic charge as well aswith coal and additives, noting that it is known to supply in thisKVA-process the required melting heat by means of burners being operatedwith natural gas and oxygen. The melting crucibles having been proposedup till now for the KVA-process comprise a taphole on the bottom, whichtaphole does, however, not provide the possibility of simple continuousoperation. In these known processes it has already been possible to movemobile ladles in a position below the taphole, thereby dischargingtogether with the molten bath also the slag and effecting slag removalfrom the subsequent ladle. On account of the taphole being provided onthe bottom of the receptacle, only a small amount of slag could beretained within the melting receptacle or, respectively, meltingcrucible even in case of a tiltable melting crucible, so that, whenperforming the melting process on a continuous basis, a correspondingamount of slag had to be produced for the purpose of obtaining aconstant quality.

SUMMARY OF THE INVENTION

The invention now aims at providing a process of the initially mentionedtype which provides the possibility to perform the melting process on acontinuous basis and with a constant quality of the bath. For solvingthis task, the process according to the invention essentially consistsin that the converter is heated in proximity of the bottom withsub-stoichiometric burners having their flames essentially radiallydirected into the interior of the converter, in that secondary air or O₂is supplied at a distance above the burner plane for the purpose ofcompleting the combustion, in that the melt is, optionally together withslag, discharged into a mobile ladle via a tapping means laterallyconnected to the converter and in that the converter is, forinterchanging ladles, swivelled into a position in which the level ofthe molten material is located below the taphole. On account of theconverter being heated in proximity of its bottom withsub-stoichiometric burners having their flames oriented in substantiallyradial direction into the interior of the converter, the ratio betweennatural gas and oxygen can, in particular when using burners beingoperated with natural gas and oxygen, be controlled in such a mannerthat the desired flame temperatures and the desired degree of oxidationis obtained. The use of sub-stoichiometric burners results in improvingthe yield in iron and in reducing the oxidation losses. On account ofnow supplying secondary air or oxygen at a distance above the burnerplane for the purpose of completing the combustion, the chemically boundheat is substantially completely utilized and the continuously suppliedcharge is preheated to a high extent, so that the process isaccelerated. The unburnt proportion of fuel is, by means of controllableamounts of air as far as possible burnt within these post-combustionnozzles, so that the scrap column is preheated in this manner. Onaccount of discharging the melt, optionally together with slag via atapping means laterally connected to the converter into a mobile ladle,there is provided the possibility to retain within the converter, whenswivelling the same, a sufficient amount of slag, so that the continuousmelting process is in no manner disturbed after having interchanged themobile ladle and having swivelled back the converter. Slag havingoptionally been discharged together with the molten bath can beseparated in the receiving ladle just located below the converter,noting that the laterally protruding tapping means allows to retainwithin the converter a sufficient volume of slag already in case ofsmall tilting angles. It is possible to retain within the converter themetallic material still subjected to the melting process also wheninterchanging the ladles, thereby maintaining the continuity of theprocess, for which purpose it is already sufficient to tilt theconverter, when interchanging ladles, into a position in which the levelof the melt is located below the taphole.

The inventive apparatus for performing this process has a converter andis essentially characterized in that a plurality of burner nozzlesextending in essentially radial direction is arranged on the converterwithin a plane located in proximity of the converter bottom, in that airnozzles are arranged within a further plane located at a higher leveland in that a jutty-shaped tapping means is connected to the convertervia a radial taphole. It is of substantial importance for the apparatusaccording to the invention that the jutty-shaped tapping means isconnected to the converter by a radial taphole, said tapping meansimproving the kinematics of the tilting operation inasfar asinterchanging of ladles without dripping becomes possible also in caseof small tilting angles. This embodiment is advantageously furtherdeveloped such that the jutty-shaped tapping means has a substantialradial channel being in alignment with the radial taphole of theconverter and that a tapping channel extending in essentially parallelrelation to the axis of the converter is connected to the substantiallyradial channel, noting that such an angular design of the channelswithin the tapping means provides the possibility to do with only smalltilting angles when interchanging ladles and provides the possibility toarrange auxiliary equipment warranting the continuity of the process.Thereto, the jutty-shaped tapping means comprises at least one burnerwhose flame is directed in one of both respective channels. Such burnersbeing connected to the jutty-shaped tapping means prevent solidificationof the molten bath within the channels during the stage of interchangingladles, which solidification might cause an interruption of thecontinuous process. In this case, it is of advantage to direct burnersinto both channels, i.e. into the substantial radial channel being inalignment with the radial taphole of the converter as well as into thefurther channel being arranged at an angle relative to said firstchannel, so that a homogenous temperature distribution is reliablyestablished.

It is of advantage to select the arrangement according to the inventionsuch that the channel, which is connected to the radial taphole of thetapping means, has a greater free cross section than the channel, whichis parallel relative to the axis of the converter, of the tapping means,so that there is provided the possibility to connect burners to a spacebeing free of melt of the substantially radial first channel. In thiscase, it is possible to keep the burner nozzles free of any directinfluence of the molten bath and, in this case, the arrangement is in aparticularly simple manner selected such that there are connected tothat channel of the tapping means which is connected to the radialtaphole two burners with mutually crossing or intersecting flame axesand a closeable sampling opening. The additionally provided samplingopening entering this channel, provides the possibility to continuouslymonitor the process and to control the burners of the converter in acorrespondingly desired manner.

Particularly rapid interchanging of the mobile ladles is made possibleif the arrangement is such that the exit end of the tapping channel ofthe jutty-shaped tapping means carries a cover for the ladle beingmovable in a position below the tapping channel, said cover beingtiltable in common with the converter and being adapted for being liftedoff the ladle. On account of the cover of the subsequent ladle beingconnected with the converter or, respectively, the jutty-shaped tappingmeans, changing of the ladle can be effected in a particularly rapidmanner, so that the process is interrupted for only a very smallinterval.

The burners of the converter are preferably operated with oxygendeficiency, which results in a λ-value of 0.8 to 0.9. The non-burntportions of the natural gas, in particular CO und CH₄, flow, togetherwith the effluent gases, in upward direction and are completely burntwithin the area of the plane for supplying secondary air. As comparedwith a shaft furnace, the use of a converter allows simple tiltingmovement when changing the ladle, and the apparatus according to theinvention may directly be obtained in practice by changing theconstruction of existing converters, for example by changing theconstruction of LD-converters. As compared with known tiltable furnaceconstructions, the tiltable suspension of the converter provides for asubstantially improved accessibility of the space below the converter,noting that such circumstantial manipulations as are required inconnection with tapholes arranged on the bottom of converters areavoided on account of the jutty-shaped tapping means having burnersincorporated therein.

BRIEF DESCRIPTION OF THE DRAWING

In the following, the invention is further explained with reference ofthe FIGURE of the drawing schematically showing an example ofembodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In the drawing, there is shown a tiltable converter 1, the swivellingaxis of which is designated by the reference numeral 2. Gas burners 4operated with natural gas are connected to the converter via an annularconduit and in proximity of the converter bottom, the flames 5 of saidburners being essentially radially directed into the interior of theconverter. The converter 1 can continuously be charged with scrap 6, forwhich purpose there is provided a charging chute 7.

Above the burner plane being formed by the burners 4, there is arrangeda further annular conduit 8 for the supply of secondary air. On accountof the burners 4 being sub-stoichiometrically operated with a λ-value of0.8 to 0.9, the supplied fuels are completely burnt within the plane ofsecondary air.

A jutty-shaped tapping means 9 comprising an essentially radial channel10 is connected to the converter bottom 3. This radial channel 10 of thejutty-shaped tapping means 9 is in alignment with a radial taphole 11 ofthe converter 1 and passes over into a channel 13 extending inessentially vertical direction and in parallel relation to the axis 12of the converter 1. The substantially radial channel 10 has a greaterfree cross section than the tapping channel 13 extending in parallelrelation to the axis 12, so that the radial channel 10 need notcompletely be filled when discharging the molten bath. It is ofadvantage if a free space is present above the outwardly flowing melt 14and if burners 15 and 16 open into this free space and have the burneraxes intersecting one another. The burner 15 serves the purpose ofheating the radial channel 10, whereas the burner 16 prevents cloggingof the vertical channel 13 by solidificating metal.

A sampling opening 17 is additionally connected to the radial channel10, said sampling opening allowing to control the melting process.

A cover 18 is connected with the jutty-shaped tapping means 9 and can beswivelled in upward direction around the swivelling axis 2 together withthe converter 1 and the jutty-shaped tapping means 9 if the ladle 19having been moved therebelow shall be interchanged. The ladle 19 itselfcan be moved on rollers 20, and a separate slag receiving receptacle 21is mounted on the chassis of the ladle 19 for the purpose of slagseparation.

What is claimed is:
 1. Apparatus for continuously forming a melt ofscrap and/or pig iron and for discharging the melt into a mobile ladle,said apparatus comprising:A converter having a bottom, radical tapholeand an interior; a plurality of burners (4), extending in essentiallyradial direction relative to said converter and arranged on theconverter (1) within a first plane having an orientation parallel tosaid bottom of the converter and being located in proximity to saidbottom (3) of the converter, for directing flames into the interior ofthe converter for sub-stoichiometric heating there; a plurality of airnozzles arranged within a further plane located above the first planefor supplying secondary air for completing combustion; and tapping means(9) for discharging the melt from said converter into the mobile ladle(19), said tapping means being connected to the bottom of the convertervia said radial taphole within the converter.
 2. Apparatus as claimed inclaim 1, wherein the tapping means (9) has a channel (10), alignedrelative to said taphole of the converter and in a directionsubstantially radial relative to the converter, and a tapping channel(13) extending in essentially parallel relation to a vertical axis (12)of the converter (1) and being connected to the radially directedchannel (10).
 3. Apparatus as claimed in claim 1 or 2, wherein thetapping means (9) comprises at least one burner (15, 16) located suchthat its flame is directed towards one of said channels (10, 13) of thetapping means (9).
 4. Apparatus as claimed in claim 2, wherein theradially directed channel (10) has a greater cross section than thetapping channel (13).
 5. Apparatus as claimed in claim 1 or 2, whereinthe tapping means (9) includes a cover (18) for the ladle (19) which ismovable to a position below the tapping channel (13), said cover (18)being disposed at an exit end of said tapping means and being swivelablein common with the converter (1), said cover being adapted to be liftedoff the ladle.
 6. Apparatus as claimed in claim 3, wherein the tappingmeans further comprises:first and second burners (15, 16) located suchthat their flames are directed to intersect within said radiallydirected channel; and a closable sampling opening connected to saidradial channel.